Golam Mowla, Nabid Hossain, M. Humayan Kabir, M. Jahidul Haque, M. Mintu Ali, M. Abdul Kaiyum, M. S. Rahman
In the present work, pure BaTiO3, pure Ni0.6Zn0.4Fe2O4 and (1-x)BaTiO3-xNi0.6Zn0.4Fe2O4 (where x = 0.15, 0.25 & 0.35) multiferroic composites were synthesized through solid-state sintering scheme. Structural, microstructural, ferroelectric, and ferromagnetic analysis was performed. Both tetragonal perovskite phase (for BaTiO3 ferroelectric phase) and cubic spinel ferrite phase (for Ni0.6Zn0.4Fe2O4 ferromagnetic phase) were simultaneously presented within each composite. The ferrite phase exhibited a smaller crystallite size compared to the ferroelectric phase. All of the composites demonstrated homogenous irregular-shaped grains. The measured average grain size for 0.85BaTiO3-0.15Ni0.6Zn0.4Fe2O4, 0.75BaTiO3-0.25Ni0.6Zn0.4Fe2O4, 0.65BaTiO3-0.35Ni0.6Zn0.4Fe2O4 were 364.14 nm, 378.46 nm and 351.62nm, whereas the density values were 3.04g/cm3, 3.20g/cm3 and 3.13 g/cm3 for x = 0.35, 0.25, 0.15 respectively. However, the heterogenous microstructure was observed for all of the compositions. The composites exhibited an oval-shaped lossy capacitor hysteresis loop. However, 0.75BaTiO3-0.25Ni0.6Zn0.4Fe2O4 composite showed the highest remnant polarization (11.613 μC/cm2) and coercive field value (1.526 kV/cm), ensuring its usability for switching applications. In addition, 0.75BaTiO3-0.25Ni0.6Zn0.4Fe2O4 also exhibited the maximum saturation (Ms= 1.732 emu/g) and remnant magnetization (Mr= 0.025 emu/g) among the composites. Nevertheless, all of the composites derived 'wasp-waisted' hysteresis loops due to the presence of either superparamagnetic (SPM) particles or a mixer of a single domain (SD) and superparamagnetic particles.
In this study, zinc oxide (ZnO) nanoparticles (NPs) were first synthesized using co-precipitation method in the presence of Zn(NO3)2.6H2O precursor and calcined at different temperature of 450 oC and 1000 oC. Samples were then characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The XRD study revealed the hexagonal wurtzite structure for annealed samples. SEM images showed tthat he morphology of the ZnO NPs changed from sphere-like shape to polygon shape by increasing temperature. The exact size of NPs were measured by TEM analysis about 40 nm for as-prepared samples. The EDS analysis demonstrated an increasing level of Zn element from 28.5 wt% to 50.8 wt% for as-synthesized and annealed samples, respectively.